1. Field of the Invention
The present invention is related to a reset circuit, especially a reset circuit of a microcomputer to which a drive voltage is supplied from a switching power circuit that executes feedback control.
2. Description of the Related Art
In an electronic device, a power supply status is easily changed. Therefore, in order to drive the electronic device correctly, a microcomputer to control the electronic device should be surely reset when the power supply of the electronic device is reduced. Japanese Patent Application Publication No. 2010-186336 discloses a technology in which a control microcomputer driven by a secondary voltage of a DC/DC converter is switched to reset state by a power control computer when a voltage detection circuit detects a reduction of the power supply. Japanese Patent Application Publication No. H10-293142 discloses a technology of a microcomputer that is supplied power from a battery and can detect the voltage of the battery by the microcomputer itself. Japanese Patent Application Publication No. 2008-219658 discloses a technology of a microcomputer that outputs a signal to turn off a power supply circuit when the microcomputer detects reduced voltage state for a certain period.
In the above described conventional reset circuits, a microcomputer plays a certain role when detecting the reduction of the power supply. Therefore, there is a problem of reliability as to a timing when the microcomputer is reset.